pfSense is set up to block everything by default on the WAN, LAN has default allow, so LAN devices can access anything and WAN devices cant, also its top down for rules so if you have a block rule at the top but an allow rule below that, block all takes priority.
What are you trying to do?

You don't need add a default block rule on LAN, the LAN interface is "block everything" by default just like any other interface.

What XIII says about "allow all" on LAN isn't quite correct, on the default configuration there is an "allow all" rule on LAN interface that allows all traffic but that rule isn't hidden and can be changed or deleted.